The invention relates to anchors for securing a device to a substrate, and more particularly to anchors for securing a Micro-Electro-Mechanical Systems (MEMS) device to a substrate.
Micro-Electro-Mechanical System (MEMS) devices find applications in a variety of fib fields, such as communications, sensing, optics, micro-fluidics, and measurements of material properties. In the field of communications, MEMS Radio Frequency (RF) switches and variable MEMS capacitors are used in tunable RF filter circuits. The MEMS RF switches and MEMS capacitors offer several advantages over solid state varactor diodes, including a higher on/off capacitance ratio and higher Quality (Q) factor.
A MEMS device is typically secured to a substrate by an anchor. The xe2x80x9cfootprintxe2x80x9d area of a traditional anchor is maximized with respect to a set of design rules and process constraints to assure proper adhesion of the MEMS device to the substrate. The anchor must be strong enough to withstand stress exerted on the anchor by bending or flexing of the MEMS device. A drawback of the traditional anchor is that the strength of the anchor is increased by increasing the xe2x80x9cfootprintxe2x80x9d area of the anchor, which has the undesirable affect of increasing the overall size of the MEMS device, or otherwise places additional design constraints on the MEMS device. Another drawback is that a single fracture in the traditional anchor can propagate along the length of the anchor resulting in mechanical failure of the anchor.
The present invention provides an anchor system for securing the base of a MEMS device to a substrate comprising multiple anchors instead of a traditional anchor that maximizes the xe2x80x9cfootprintxe2x80x9d area of the anchor. By segmenting the anchor system into multiple smaller anchors, the invention is able to increase the overall strength of the anchor system.
A MEMS structure, built in accordance with one embodiment of the invention, comprises a flexible beam suspended over a substrate and a base attached to each end of the beam. Each base is supported above the substrate by multiple anchors attached to the surface of the substrate. Each anchor further comprises anchor legs along its sides that support the respective base off of the substrate.
In one embodiment, the anchors of each base are located away from the interface between the beam and the base. This is done so that stress due to bending or flexing of the beam occurs away from the anchors, thereby making the anchors less prone to mechanical failure.
In another embodiment, the lengths of the anchor legs of the anchors are made longer along a direction of good side-wall step coverage than along a direction of poor side-wall step coverage. This is done to increase the overall strength of the anchor system when a metal deposition process that provides better side-wall step coverage in one direction than another direction is used to fabricate the anchors.
Other objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.